Which of the following is NOT typically used to evaluate system reliability in MDC3?

• A. Uptime
• B. MTTR
• C. Customer satisfaction score
• D. MTBF

Answer: (C)

Reliability is about how consistently the system performs when needed and how quickly it recovers from issues. Uptime directly measures how much time the system is operational, making it a primary indicator of reliability. MTTR, the average time to repair, shows how fast you can restore service after a failure, which is crucial for understanding system resilience. MTBF, the mean time between failures, indicates how often failures occur, another core reliability metric. In contrast, customer satisfaction score gauges user-perceived quality across many factors, not just the system’s failure and recovery behavior. It reflects broader impressions like performance, usability, and support, so it isn’t a direct measure of reliability. So the metric that isn’t typically used to evaluate system reliability is the customer satisfaction score.